The class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon has been known for some time. Such polymers were produced by Nozaki, e.g., U.S. Pat. No. 3,694,412, using arylphosphine complexes of palladium moieties as catalysts and certain inert solvents. More recent methods for the production of such linear alternating polymers, now known as polyketone polymers or polyketones, are illustrated by a number of published European Patent Applications including Nos. 121,965, 181,014, 213,671 and 257,663. The processes generally involve the use of a catalyst composition formed from a compound of palladium, cobalt or nickel, the anion of a strong non-hydrohalogenic acid and a bidentate ligand of phosphorus, arsenic, antimony or nitrogen.
The polyketone polymers are relatively high molecular weight materials having established utility as premium thermoplastics. The polyketone polymers are processed by techniques conventional for thermoplastics, e.g., injection molding, extrusion or thermoforming, into shaped articles of established utility.
Although the scope of the polymerization to produce polyketone polymers is extensive, a preferred catalyst composition is formed from a compound of palladium, the anion of a non-hydrohalogenic acid having a pKa below 2 and a bidentate ligand of phosphorus. Although each of the catalyst composition components has a considerable influence on the activity of the catalyst formed as well as upon the properties of the polymer produced by the polymerization process employing such a catalyst composition, the nature of the bidentate phosphorus ligand appears to be particularly important. Among the preferred bidentate phosphorus ligands of early processes were bis(hydrocarbyl aryl)phosphinoalkanes such as 1,3-bis(diphenylphosphino)propane. Somewhat later, it was found that better results were obtained when each monovalent phosphorus substituent contained a polar group, particularly an alkoxy group such as methoxy. Particularly useful were bidentate phosphine ligands wherein each monovalent phosphorus substituent was phenyl with an alkoxy substituent on an aromatic ring carbon atom ortho to the carbon atom through which the substituent is connected to the phosphorus. An example of a particularly preferred bidentate ligand of this type is 1,3-bis[di(2-methoxyphenyl)phosphino]propane. Such substituted-phenyl diphosphines, although providing catalyst compositions which result in faster reaction rates and higher molecular weight product, are somewhat more difficult to prepare.
In published European Patent Application 296,687 there is described a class of bidentate ligands wherein the divalent aliphatic linking group joining the two phosphorus atoms is alkylene disubstituted with alkyl or other substituents. Illustrative of such ligands are 2,2-dimethyl-1,3-bis(diphenylphosphino)propane and 2,2-dimethyl-1,3-bis[di(2-methoxyphenyl)phosphino]propane. The presence of disubstitution in the alkylene linking group provides catalyst compositions which give good results regardless of whether the monovalent phosphorus substituents are hydrocarbyl or polar-substituted hydrocarbyl. It would be of advantage, however, to provide additional bidentate ligands of phosphorus, the use of which results in catalyst compositions which afford polyketone polymers at higher polymerization rates and with higher molecular weight polymer.